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SYNTAX ERROR: Difference between revisions
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A SYNTAX ERROR is an [[error message]] which indicates that a rule of [[APL syntax]] was violated. A SYNTAX ERROR may indicate an ill-formed expression which violates APL's grammar: | A SYNTAX ERROR is an [[error message]] which indicates that a rule of [[APL syntax]] was violated. A SYNTAX ERROR may indicate an ill-formed expression which violates APL's grammar: | ||
< | <syntaxhighlight lang=apl> | ||
( | ( | ||
SYNTAX ERROR | SYNTAX ERROR | ||
| Line 10: | Line 10: | ||
'Hello world | 'Hello world | ||
∧ | ∧ | ||
</ | </syntaxhighlight> | ||
However, a SYNTAX ERROR may also indicate a problem not with the sequence of tokens in a statement, but with their meaning. For example, below an error results when a [[function]] is called with invalid [[valence]]: here, a [[monadic function]] with two arguments. | However, a SYNTAX ERROR may also indicate a problem not with the sequence of tokens in a statement, but with their meaning. For example, below an error results when a [[function]] is called with invalid [[valence]]: here, a [[monadic function]] with two arguments. | ||
< | <syntaxhighlight lang=apl> | ||
fn ← + | fn ← + | ||
2 fn 3 | 2 fn 3 | ||
| Line 21: | Line 21: | ||
2 fn 3 | 2 fn 3 | ||
∧ | ∧ | ||
</ | </syntaxhighlight> | ||
Depending on the value of < | Depending on the value of <syntaxhighlight lang=apl inline>fn</syntaxhighlight>, the same statement may or may not be considered invalid syntax. This is to be expected, since APL does not have a [[wikipedia:context-free grammar|context-free grammar]] and needs to know the type of each variable to parse a statement. | ||
{{APL features}} | {{APL features}}[[Category:Errors]] | ||