∇z ← a F b
[1]   z ← a ×÷ b
∇

[...]

     )si
      0 F 0
DOMAIN ERROR
F[1]  z←a×÷b
          ^^
      ⎕L
VALUE ERROR+
      ⎕L
      ^
      ⎕L 3

==============================================================================
Assertion failed: size() > 0
in Function:      at0
in file:          Prefix.hh:143

C/C++ call stack:

----------------------------------------
-- Stack trace at Assert.cc:72
----------------------------------------
0x7F82F75607FD __libc_start_main
0x55C23F9D75C5  main
0x55C23FBB7975   Workspace::immediate_execution(bool)
0x55C23FA5A051    Command::process_line()
0x55C23FA5A113     Command::finish_context()
0x55C23FA69C08      Executable::execute_body() const
0x55C23FB49F4C       StateIndicator::run()
0x55C23FAB2076        Prefix::reduce_statements()
0x55C23FB6024D         Symbol::resolve(Token&, bool)
0x55C23FB6C5FF          Quad_L::get_apl_value() const
0x55C23FB4A394           StateIndicator::get_L(UCS_string&)
0x55C23FAB2725            Prefix::locate_L(UCS_string&)
0x55C23FAA5683             
0x55C23F9F6861              do_Assert(char const*, char const*, char const*, int)
========================================

SI stack:

Depth:      3
Exec:       0x55c240955070
Safe exec:  0
Pmode:      ◊  ⎕L 3
PC:         1 (4) ⎕L
Stat:       ⎕L 3
err_code:   0x0

Depth:      2
Exec:       0x55c240959c20
Safe exec:  0
Pmode:      ◊  ⎕L
PC:         0 (3) ⎕L
Stat:       ⎕L
err_code:   0x30001
thrown at:  SystemVariable.cc:474
e_msg_1:    'VALUE ERROR+'
e_msg_2:    '      ⎕L'
e_msg_3:    '      ^'

Depth:      1
Exec:       0x55c240951a10
Safe exec:  0
Pmode:      ∇ F[1]
PC:         3 (8) 'a
Stat:       z ← a ×÷ b
err_code:   0x50004
thrown at:  ScalarFunction.cc:140
e_msg_1:    'DOMAIN ERROR'
e_msg_2:    'F[1]  z←a×÷b'
e_msg_3:    '          ^^'

Depth:      0
Exec:       0x55c240951570
Safe exec:  0
Pmode:      ◊  0 F 0
PC:         3 (5) ENDL
Stat:       0 F 0
err_code:   0x0


==============================================================================