IF - source-solutions/HELP GitHub Wiki

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IF truth_value {THEN|GOTO} [compound_statement_true|line_number_true [anything]][ELSE [compound_statement_false|line_number_false [anything]]]

If truth_value is non-zero, executes compound_statement_true or jumps to line_number_true. If it is zero, executes compound_statement_false or jumps to line_number_false.

• truth_value is a numeric expression.
• line_number_false and line_number_true are existing line numbers.
• compound_statement_false and compound_statement_true are compound statements, consisting of at least one statement, optionally followed by further statements separated by colons (:). The compound statements may contain nested IF to THEN to ELSE statements.

• The comma is optional and ignored.
• ELSE clauses are optional; they are bound to the innermost free IF statement if nested. Additional ELSE clauses that have no matching IF are ignored.
• All clauses must be on the same program line.
• THEN and GOTO are interchangeable; which one is chosen is independent of whether a statement or a line number is given. GOTO PRINT 1` is fine.
• As in GOTO, anything after the line number is ignored.

• If truth_value has a string value: Type mismatch.
• truth_value equals 0 and line_number_false is a non-existing line number, or truth_value is nonzero and line_number_true is a non-existing line number: Undefined line number.