7.4.67. TRACE

Returns trace actions currently in effect and, optionally, alters the setting.

If you specify option, it selects the trace setting. It must be the valid prefix ?, one of the alphabetic character options associated with the TRACE instruction (that is, starting with A, C, E, F, I, L, N, O, or R), or both. (See the TRACE instruction in Section 2.29.1, “Trace Alphabetic Character (Word) Options” for full details.)

Unlike the TRACE instruction, the TRACE function alters the trace action even if interactive debugging is active. Also unlike the TRACE instruction, option cannot be a number.

Here are some examples:

Example 7.92. Builtin function TRACE

Say TRACE()       -->   "?R" /* maybe */
Say TRACE("O")    -->   "?R" /* also sets tracing off */
Say TRACE("?I")   -->   "O"  /* now in interactive debugging */