Error messages

An error shows in red at the part of the statement that caused it. The command line prints it after #!. Every statement that uses a broken definition says so, naming where the trouble started:

As text

a := b + 1
c := a + 1

Open this example · Download .bbm

Fix the first one, and the rest follow.

Names

b is not defined

Nothing above defines b. The sheet is worked out top to bottom, then left to right, so a definition below or to the right of its use doesn’t count yet: move it up. Check the spelling, the case (F is not f), the subscript, and the style (a bold F is a different name from F).

x is defined globally (≡); it can't be redefined

A global definition (≡, typed ~) holds for the whole sheet, so it can’t be defined again with :=. Use another name, or make the global an ordinary definition.

A result is wrong by a large factor

Look for a variable named like a unit. After m := 2 kg, 3 m is 6 kg, not three metres, for everything below. Beermat warns, in orange under the statement: m here is the variable defined above, not the unit m. Rename the variable (M, m_1, mass).

Units

units do not match: L vs T

Two things of different kinds are added, subtracted or compared, here a length and a time. The letters are the dimensions: L length, M mass, T time, I current, Θ temperature, N amount of substance, J luminous intensity (and ∠ angle, ¤ money, when a sheet makes them dimensions). Usually a term or a unit is missing.

units do not match: the result is L, the unit is L·M·T^-2

The unit typed in the result’s placeholder is of another kind than the result: here a length asked to show in kN. Change the unit, or check the formula.

sin: the argument must be dimensionless or an angle, not L

Functions such as sin, exp and ln need a plain number. Divide by a unit, or check the formula.

an exponent must be dimensionless, not L

A power must be a plain number: x^2, not x^(2 m).

Typing

missing operator before '3': write '*'

Two numbers side by side. Only a name may follow a number without * (2 m, 2 x).

missing ')'

A bracket was opened and not closed.

expected '?' after '=' (write 'x = ?' to evaluate, or '==' to compare)

In a file, = shows a result and must be followed by ?. To compare, use == (Ctrl+= in the app).

this definition needs a name

The left of := is still empty.

Arrays and ranges

i is a range variable: it can define the elements of an array (v[i] := …), not a single value

A range variable stands for each of its values in turn, so y := i^2 has no single value. Define the elements instead: y[i] := i^2.

row 2 is out of range: there are 2, numbered from ORIGIN = 0

Indices count from ORIGIN, 0 unless the sheet sets it. The last element of a vector of 2 is v[1].

cannot multiply a 2×2 matrix by a 1×3 matrix: the columns of the first must match the rows of the second

A matrix product needs matching sizes. For an element-by-element product, use vec(a*b). A transpose (^T) may be what’s missing.

mean: expected a number, not a string

The function needs numbers (or arrays of them), and was given text in quotes. Functions that take one number, such as sqrt and sin, work on every element of an array by themselves: sin(v).

Calculations

division by zero

Dividing by 0 is an error, not infinity. try … on error … can catch it where it is expected.

f takes 1 argument(s), not 2

The call has a different number of arguments from the function’s definition.

too many nested calls (is the recursion infinite?)

A function calls itself without end. Check that it has a case that stops: fact(n) := if(n < 1, 1, n*fact(n - 1)).

the while loop ran more than 10000000 times (does its condition ever become false?)

The loop’s condition never changes. Check what the loop changes.

an operand must be a number, not a string

Text can be compared (==) but not used in arithmetic. concat joins texts, num2str and str2num convert.

Solving

root: no root found near the guess (give limits: root(f, x, a, b))

There may be no real root, or it is far from the guess. Plot the function to see where it crosses zero, then give limits on either side of it.

find: no solution found from these guesses (try other guesses, or minerr for the closest values)

The conditions can’t all be met from where the search started. Try other guesses (not all equal, if the problem is symmetrical), or minerr to see how close it gets.

Python

beam_tools.py runs Python code, which hasn't been allowed yet

A sheet’s Python file runs only once you allow it. The app asks; on the command line, add --allow-python.

add: a takes a plain number; give it a unit in the .py file (a: "m"), or divide by one at the call

The function’s argument has no unit in its annotation, but was given a value with one. See Python.