16 Messages you will meet
Builds on: Chapters 1 to 15. A chapter to look things up in.
Questions this chapter answers
- The processor refused my program. What does the message mean, and how is it fixed?
- The program stopped while running. What does the name of the fault mean?
A message has the form file:line:column: reason. Lines and columns count from 1, and the column is the byte position in the line. The processor reports the first mistake it meets, so after a fix the next one may show. The messages below are exactly what the processor prints; the chapters in the right column have examples that produce them.
16.1 The stack and types
| Message | Meaning and fix | Chapter |
|---|---|---|
an argument has another type than the word's signature asks for | A value given to a word has another type than its signature asks. Read the signature, and convert the value or fix the order. | 3 |
this word takes a str, this word takes an int | That word takes that one type. A number becomes text with str.to_str, text becomes a number with str.to_int. | 5 |
the two values compared must have the same type | A comparison such as eq or lt got two values of different types. Convert one; int and dec are different types too. | 2 |
two dec values of different scales: rescale one first (d 2 rescale) | Decimals with different numbers of digits after the point, like 4.20 and 0.5. rescale one, or write both with the same digits. | 2 |
a declared type is added to and subtracted from its own type, and multiplied, divided or taken modulo by an int; for other arithmetic take raw | Arithmetic a declared type (such as cents) does not allow. Take the integer out with raw and compute with it. | 10 |
the two branches of this if leave different stacks | The two branches of an if leave different counts or types. Make both leave the same. | 4 |
this block must leave the stack as it found it | The block of a combining word such as each left a value. Use it inside the block, or drop it. | 4 |
stored text is str(N); a str view lives only in locals, arguments and results | A str was put where a global, a cell or a field lives. Places that live long take str(N). | 5 |
the stack does not hold enough values for this word | The word takes more values than the stack holds. Check that the values were put on first, and in the right order. pnx see shows the stack after each line. | 2, 15 |
values are left on the stack at the end of the source | A value that nothing took is left when the program ends. Print it, drop it, or add the word that was forgotten. | 2 |
the stack does not hold exactly the results of the signature here | What is left when the body of a word ends differs from the results of its signature. Write the results into the signature, or clear what is left. | 3 |
this word takes two int values, or two of the same declared type | An arithmetic word got another type. Text becomes a number with str.to_int, a number becomes text with str.to_str. | 2 |
an if without else must leave the stack as it found it | An if without else leaves a value. Add an else branch that leaves a value of the same type. | 4 |
one turn of a loop must leave the stack as it found it | One turn of a loop leaves or takes a value. Keep what it makes in a local with to NAME. | 4 |
inputs are all named or all bare types, not a mix | A signature mixes named inputs and inputs given as types only. Name them all. | 3 |
16.2 Characters and literals
| Message | Meaning and fix | Chapter |
|---|---|---|
this character is not allowed outside literals and remarks | A symbol such as +, ; or { is in the code. Arithmetic and separation are all words: add, mul, a line break. | 1 |
a sign is attached to its number; arithmetic uses words (add, sub) | Written like 3 - 1. A - is only the sign of a number; write 3 1 sub. | 2 |
unknown escape; a raw string r"..." keeps backslashes as written | An ordinary string holds an escape such as \d. Patterns go into raw strings r"…". | 12 |
rx takes a string literal or a const name; a pattern made while running is rex.compile | A variable was given to rex.rx. A pattern is a literal or a const; one made while running is rex.compile. | 12 |
16.3 Names
| Message | Meaning and fix | Chapter |
|---|---|---|
no module of this name is registered or loaded | The module of use is not there. Check the names of the standard and host modules; for a file module, that NAME.pnx lies beside the program. | 10 |
the module exports nothing of this name | The module has no such name, or did not export it. Add export in the module file. | 10 |
this name is already defined | A word or a declaration of that name exists already. Use another name. (In a session, word with the name of a word of an earlier line redefines it.) | 3, 15 |
this parameter takes one row of a table; a parameter that takes the whole table is written list RECORD or array RECORD | A table’s name as a parameter type means one row. To take the whole table write list RECORD or array RECORD. | 6 |
the collection given here is of another kind, or holds another type, than the parameter says | The collection given differs from the parameter in kind or element type: an array int or a list str(8) cannot stand where list int is asked for. | 6 |
this name is not declared before this place | The name does not exist, or is used before it is declared. Check the spelling and where it is declared; words that call each other use forward word. | 1, 3 |
this path names neither a module in use nor a record | The module of module.word was not opened. Write use module at the top of the file. | 1, 10 |
this name is already visible here; a new name may not hide it | A visible name of the program (a word, a global, a constant, a local outside) was used for a new name. Choose another. | 3 |
NAME is a word of the language; choose another name | A word of the language — a reserved word, a core word such as sum, count or first, a word such as sort, a type — was used for a new name, wherever the name was made. Choose another. | 3 |
rows do not move: sort a list of their numbers by a field: order table sort_by record.field | sort was given a table of records. Fill a list with the rows (list order cities 8) or their numbers and sort it with sort_by. | 7 |
outside a definition +“to”+ makes no new local; a global is written with set | to was used outside a definition, where there are no locals. Put the work into a word, or store into a global with set. | 4 |
this name is a global; a global is written with set: value set name | A global, or a cell of a global collection, was stored into with to. Write value set name; a cell is value i set name. | 4, 6 |
16.4 Failures and owned values
| Message | Meaning and fix | Chapter |
|---|---|---|
an owned value in a local is not given on every path (close, free or store it) | An owned value (an open file, a row of a pool, a mark) is not handed on along some path. Look at the ways out on failure and at return too; defer makes this easy. | 9 |
this local gave its owned value away; it holds nothing to read | The name was used again after its value was handed on. A closed file cannot be used. | 9 |
a defer gives this owned value when the block is left; here it can only be lent | A value left to defer was handed on (closed) in the body as well. Leave the closing to defer and only lend the value in the body. | 9 |
this str was made after a mark that was released since; the region may hold other bytes there now | Text made between a mark and its release was read after the release. Text to keep goes into str(N) or a buffer before the release. | 5, 9 |
or fail in its signature | The word using or_fail has no or fail in its signature. Add it, or handle the failure there with or_else. | 8 |
this list's rows are kept by a field, a global, a collection, a named row or an index; it cannot be truncated | A list whose rows are held by something cannot be truncated. Check before adding instead. | 11 |
a word that can fail is followed by or_fail, or_return or or_else | A word that can fail (push, str.to_int, a word with or fail in its signature) has no guard after it. Even to ignore the failure, write or_else (e) end. | 6, 8 |
the body of or_else must leave what the word would have given, or leave the word or the loop | The body of or_else leaves other values than success would. Leave a stand-in of the same type, or leave with return or break. | 8 |
an owned value is kept in a local or given on at once; this word would lose it | An owned value is about to be lost with drop, or left on the stack. Keep it in a local and close it at the end (defer makes it easy). | 9 |
a field holds str(N); a str view lives only in locals, arguments and results | A view str was used for a field or a global. Declare it str(N). | 5 |
16.5 When a run stops: faults
A program that loaded can still stop with a fault while it runs. pnx shows the reason, the line and the locals of the word.
| Fault | What pnx says | Meaning |
|---|---|---|
overflow | integer overflow | An integer went beyond 64 bits (chapter 2). The chk_ words give it as a failure. |
div_zero | division by zero | Division by 0. |
range | index out of range | A cell number outside the length, or a field of the “none” row (chapters 6, 7). |
full | a declared capacity is used up | The region or the room of a stored text ran out (chapter 5). |
depth | call depth limit | Calls went too deep. Look for a recursion that does not end (chapter 3). |
stale | a row or handle was used after it was given back | A pool row given back, or a closed handle, was used (chapters 7, 9). |
deadlock | deadlock: waiting for a queue that nothing can change | Every task waits for a queue (chapter 13). |
Q&A
Q. Can a fault be caught inside the script?
A. No. A fault points at a place where the program has to be fixed. Where something can go wrong because of data from outside, use a word that gives a failure instead (chk_mul, str.to_int and so on) and handle it with or_else (chapter 8).
Summary
- A refusal reports the first mistake met, with
file:line:column(standard 4). - Mistakes with the stack, names, failures and
ownedvalues all show before the program runs (standard 4). - A fault is a mistake that can only be known while running, and it stops the run (11.3).