Statements

The body of a dfn is a sequence of statements, evaluated in order. Each statement is one of:

• an expression, whose value can become the result of the dfn
• a guard: an expression, a colon, and a further expression (condition: result)
• an error-guard: a vector of error numbers, the digraph ::, and a further expression (errnos:: result)
• an assignment, which binds a name local to the dfn
• a comment, introduced by ⍝

Statements are separated by the diamond (⋄) character or by newlines. A dfn returns the value of the first statement it evaluates that is not an assignment, a guard, or an error-guard, after which evaluation stops. When a guard's condition is true, its right-hand expression is evaluated and returned. An error-guard returns its right-hand expression only if a matching error occurs while the guard is in scope. If evaluation reaches the end of the dfn without producing a value, the dfn returns no result.

Example

      sign←{
          ⍵>0: 1        ⍝ guard: returned when ⍵>0
          ⍵<0: ¯1
          0             ⍝ reached only when neither guard holds
      }
      sign ¯4
¯1

Control structures and labels are not part of a dfn; conditions are expressed with guards instead (see Restrictions).