Line parsing

 

Every line input to [B/D] is parsed before being passed to the command line interpreter. The parsing consists of replacing various of the characters in the line by other characters, and of the removal of redundant spaces. In particular we use the pair of square brackets `[ ]' to enclose text that might be replaced.

All command lines have leading and trailing spaces removed. All command lines ignore other spaces (except the space separating command from arguments) and are converted to lower case. Exceptions are the PRINT: , TITLE: , PRINT: , ITITLE: , and STRING:  commands, where space and case conversions are not carried out except as necessary. Substrings are, however, parsed completely, for the STRING:  command.

The parsing of lines to replace material enclosed in square brackets takes place before any other operation. The material that might be replaced is as follows:

• Control variables defined in active FOR:  statements, such as , which will be replaced by the current value of the control integer.
• Strings defined in a STRING:  statement, such as , which will be relaced by the current contents of the string called a.
• Integers defined in an equation of the form [(E)]. That is, the equation E is calculated and then rounded to give an integer which replaces all of [(E)]. The rounding convention is defined in Appendix A.
• Quantities of the form [<B:I>], where B is the name of a base and I is a positive integer. The effect is to replace by the name of the element being the Ith element of the base B, according to the ordering convention.

Priority is decided by deepest nesting. Unrecognised quantities in [ ...] are not erased from the command line.