B4P Reference

Function Names

left , left include , left last match , left last match include

Description

This function extracts a left part of the set either with a element position number or a subset resembling a matching element.

Call as: function

Restrictions

Indirect parameter passing is disabled

Parameter count

Min 2

Parameters

No.	Type	Description
1 input	set	input set Attention: If 1st parameter is not a set, please refer to left [string function] instead.
2 input	numeral	set position Positive: Select the first n elements of the set. Larger than number of elements in the set: Full set returned Negative: Keep number of elements counted from the right (-1 = all except last element) Smaller than minus number of elements: Empty set returned Zero: Empty set returned The function name ending '... include' will be ignored. Using the function name part '... last match ...' will assert an error.
Alt. 2 input	set	matching elements Function left ...: Return the left part of the set without the matching element. Function left include ...: Return the left part of the set including the matching element. Empty sets are interpreted as no matches. The full set will be returned If this function parameter contains 2 or more elements, then the set will be compared with all elements and the first match with any of these elements will apply. Function name ending ... last match: Looks for the last matching element in the set and not the first one.
Opt. 3+ io	set	follower Other sets in addition to the one provided as the first function parameter can be extracted in the same same way. Add any number of additional set variables. They will be manipulated at the exact same positions as the returned value.

Return value

Type	Description
set	Extracted subset

Examples

               set[] = { the, taste, of, the, 12, coffees, '!' };



               echo( left( set[], 0 ), ", ", left( set[], 1 ), ", ", left( set[], -2 ), ", ", left( set[], -1 ) );

               echo( left( set[],99 ), ", ", left( set[], -99) );

               echo;

               echo( left( set[], { 12, of } ), " / ", left include( set[], { 12, of } ) ); // Recognized 'of' as 1st match

               echo( left last match ( set[], {the} ), ", ", left last match include( set[], {the} ) );

               echo( left( set[], {tea } ) ); // Returns full set because element not found



               echo( new line, "Demonstrate the follower feature: ");



               set2[] = { A, fragrance, coming, from, 120, espressos, '!' };

               set3[] = { Der, Geschmack, kommt, von, 120, Tassen Kaffee, '!' };



               echo( "Extraction 1: ", left( set[], {of}, set2[], set3[] ) );

               echo( "Extraction 2: ", set2[] );

               echo( "Extraction 3: ", set3[] );

Output

{}, {'the'}, {'the','taste','of','the',12}, {'the','taste','of','the',12,'coffees'}
{'the','taste','of','the',12,'coffees','!'}, {}

{'the','taste'} / {'the','taste','of'}
{'the','taste','of'}, {'the','taste','of','the'}
{'the','taste','of','the',12,'coffees','!'}

Demonstrate the follower feature: 
Extraction 1: {'the','taste'}
Extraction 2: {'A','fragrance'}
Extraction 3: {'Der','Geschmack'}

Try it yourself: Open LIB_Function_left_.b4p in B4P_Examples.zip. Decompress before use.

left ... (set function)