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Contents → REFERENCE MANUAL → Syntax Description → Flow Control → For Statement

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The for statement comes in two forms. The first is

for ( expression1 ; expression2 ; expression3 ) statement

The flow expressed in this statement can be thought of as

expression1
while ( expression2 ) {
      statement
      expression3
}

Any of the expressions can be missing. A missing expression2 is equivalent to

while ( 1 )

The second form of the for statement is used with associative arrays. The construction

for ( identifier in assoc-array ) statement

will run through each element of the associative array assoc_array assigning to identifier the string value of the index of each element. The elements will be sorted using a "natural sort" ." "Natural sort" means that consecutive digits are treated as a single character and sorted according to their value as a group, such that a10 will come after *a9, contrary to the order with strict lexicographical sorting.

For two-dimensional associative arrays, the construction

for ( identifier in assoc-array[expr] ) statement

will step through each element of assoc-array having expr has the first index.

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